From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9B17EC4332D for ; Fri, 20 Mar 2020 14:24:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 62D8D20781 for ; Fri, 20 Mar 2020 14:24:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QIcbvGfZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727677AbgCTOYS (ORCPT ); Fri, 20 Mar 2020 10:24:18 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:59774 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727236AbgCTOWe (ORCPT ); Fri, 20 Mar 2020 10:22:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=MRxRO1fcwbFnyNnTRcoLLuE0j9WLLNVBpiFAzDcHLGo=; b=QIcbvGfZA3PeGw0fYUhbdqz6SR RgrMY+rOF7L8CM9S/WFa2bEkx9vFrp29udQWW8L0PrK7WuSKP3z53dTw98tPq3Jgr/bDTc8eVbky6 rOUWqzb/Q4P31uLOhIH9jFMQdyagN+2MtzFHU8EEX0vgNw0AkKvjyVyZ0dBqQWhHWGbM9ub8ePtpC aae7Dk3lcGbgWNHit9uRy9lUx2vIGoqePKDT/XJaMGh78pxENGo2GIukQPX2hAn43WWr4bddZP9rH ByqFx1ZKTLHsrReJEjgiZ90r7LTz2OmBgvEOYWHJw6NndPF9D2J9yLew19Wnivz1q63l3h6+W9VGW 0RlSNrWQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jFIXh-0000iX-Nr; Fri, 20 Mar 2020 14:22:33 +0000 From: Matthew Wilcox To: Andrew Morton Cc: "Matthew Wilcox (Oracle)" , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org, Christoph Hellwig , William Kucharski Subject: [PATCH v9 14/25] mm: Document why we don't set PageReadahead Date: Fri, 20 Mar 2020 07:22:20 -0700 Message-Id: <20200320142231.2402-15-willy@infradead.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200320142231.2402-1-willy@infradead.org> References: <20200320142231.2402-1-willy@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org From: "Matthew Wilcox (Oracle)" If the page is already in cache, we don't set PageReadahead on it. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Reviewed-by: William Kucharski --- mm/readahead.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index 8ee9036fd681..0afb55a49909 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -195,9 +195,12 @@ void page_cache_readahead_unbounded(struct address_space *mapping, if (page && !xa_is_value(page)) { /* - * Page already present? Kick off the current batch of - * contiguous pages before continuing with the next - * batch. + * Page already present? Kick off the current batch + * of contiguous pages before continuing with the + * next batch. This page may be the one we would + * have intended to mark as Readahead, but we don't + * have a stable reference to this page, and it's + * not worth getting one just for that. */ read_pages(&rac, &page_pool, true); continue; -- 2.25.1